Muslim Tatars are the second largest ethnic group in Russia

The decision ends a dispute with the republic of Tatarstan, whose people speak a Turkic language quite distinct from Russian.

Most of Russia's ethnic groups use Cyrillic letters, but Tatarstan has a long-term strategy to move to Latin.

Moscow snubs such moves as evidence of separatist tendencies.

The court considered a complaint against a language law adopted earlier this year. It ruled that its provision which says that all languages native to Russia should use the Cyrillic alphabet did not contradict the constitution.

The court did not rule out the possibility of switching to another alphabet, but declared that regional authorities can not do this independently without the consent of the central government.

Changing alphabets

Tatars used the Arabic alphabet until 1927 and then transferred to Cyrillic. But in the 1990s, many of the former Soviet republics, whose people speak other Turkic languages, replaced the Cyrillic alphabet with the Latin one, as used in the Turkish language.

The government of Tatarstan now says only the Latin alphabet can fully express the full range of sounds of its language.

Tatars are the second-largest ethnic group in Russia and have enjoyed a high degree of autonomy from Moscow.

BBC regional analyst Steven Eke notes that after Stalin forcibly russified the entire Soviet Union in the late 1930s, Russian came to dominate all areas of life outside the family.

Since the collapse of the Soviet state, that situation has been reversed, with a steady decline in the use of Russian outside Russia itself.